This year’s South By Southwest dropped the tabloid glitz from 2014, acting as a proving ground for new musicians.

Though this year’s South by Southwest Festival was unwieldy as ever, with a reported 2,200 acts performing during the course of five days last week, the glut of advertising for youth-oriented products that tarnished SXSW 2014 was far less apparent this time around. And with the exception of Miley Cyrus, who hopped onstage during rapper Mike Will’s show, absent were such attention-stealing celebrities as Coldplay, Lady Gaga, Kanye West and Jay Z, all of whom performed here last year. With astute, innovative...